Spark plug



July 20, 1954 R. SCHECHTER 2,684,060

' SPARK PLUG Filed Oct. 18, 1950 flu,

l E INVENTOR 1 ROBERT SCHECHTER -BY gm y WM}.

Patented July 20, 1954 UNITED STAT asst r OFFICE ll Claim. 1

This invention relates to spark plugs adapted particularly for use ininternal combustion engines.

One of the objects of the present invention is to provide a spark plugwhich is especially suited for use with engines having relatively highcompression ratios.

Another object of the invention is the provision of a spark plug whichis suitable for use in a variety of heat ranges, and in which theinterior oi the spark plug and its insulator are protected from theeffects of excessive heat in the engine cylinder, and from theimpingement of excessive oil and gasoline droplets or products ofcombustion.

Another object of the invention is to provide a spark plug suitable foruse in engines of relatively high compression ratios which will notcause undue harmful preignition.

Still another object of the invention is the provision of a spark plugwhich may be substituted for the usual type of spark plug in an engineof relatively high compression ratio without causing substantialvariation in the compression ratio due to the size and shape of thesubstituted slug.

Still another object of the invention is to provide a spark plugelectrode element which may be combined with the conventional type ofspark plug with a minimum of effort and with simple tools.

A further object of the invention is the provision of a spark plughaving a disc-shaped central electrode provided with means whereby theperipheral gap between electrodes may be a1- tered.

A still further object of the invention is to provide a spark plugcapable of inducing a more complete mixing of the combustible vapors atthe plug by increasing turbulence.

Another object of the invention is the provision of a spark plugprovided with an electrode having an extensive surface which prolongsthe life of the device and which is practically self-cleanmg.

Yet another object of the invention is the provision of a spark plugwhich is simple, efficient, and readily manufactured.

Other objects will be apparent to those skilled in the art afterstudying the following specification together with the accompanyingdrawing illustrating various embodiments of the invention, and in which;Fig. 1 is a view in elevation of one form of spark plug, with a portioncut away to show the arrangement of the electrodes; Fig. 2 is a viewlooking upward at the bottom of the device shown in Fig. 1; Fig. 3 is aview in elevation of a modified form of spark plug, with a portion cutaway as in Fig. 1; Fig. l is a view looking upward at the bottom of thedevice of Fig. 3; Fig. 5 is a view looking upward at the bottom of amodified form of center electrode; Fig. 6 is an enlarged cross-sectionalelevation of another form of device with a portion of the centerelectrode cut away.

One of the preferred embodiments of the invention comprises an openended ground electrode shell iii, within which there is disposed in theusual way an insulating element H which provides support for a centrallydisposed electrode E2. The center electrode includes a rodshaped elementit which is embedded in, and projects from the end of the insulator H.The lower end of element it is provided with a discshaped element It.The disc M; is preferably attached at its center to the element 23, asby Welding, while its peripheral edge is disposed con- .tiguous to, butspaced from the open end of shell it. Furthermore, in order to properlyshield the interior of the spark plug the disc it should be of slightlygreater diameter than the openingin the end of the shell and ispreferably of conical configuration.

The advantages of this simple construction include the fact that aconventional spark plug may be quickly and easily converted to thepresent design, and presently available machinery may be used in makingthe article. In the case where it is desirable to convert theconventional type of spark plug, it is a simple matter to remove, or cutoff the usual projecting electrode wire which is attached to the groundelectrode shell, and to smooth down the end surface it of the shell. Aspreviously mentioned the conically shaped portion Ill may be welded tothe projecting end of the rod IE, or attached in any manner suitable forthe use to which the spark plug will be put. The conically-shaped disc Mwill usually be stamped from any metal suitable for the temperature towhich it will be exposed when in use. As a result of the stampingoperation the periphery of the disc will tend to acquire a fairly sharpedge which will assist in the production of a strong spark across theair gap when electricity is applied. Furthermore, the life of this typeof electrode is practically unlimited inasmuch as the spark will notnecessarily take place each time at the same place; consequently verylittle of the metal will be burned away and the airgap will remainpractically constant during the life of the device.

In Figs. 3 and 4 there is shown a modified form of the invention, whichincludes an open ended ground shell electrode it, insulating element ll. and centrally disposed electrode i l supported by the rod-shapedelement it. This modified form of construction is similar to thepreviously de scribed device, with the addition of a cylindricallydisposed skirt portion [6 annularly disposed the end of the shell IS.The skirt portion is relatively thin-walled by comparison with thethickness of the shell portion, and is provided with a substantiallycylindrical inner surface l! which merges upwardly and inwardly near theopening in the shell, into a curved annular surface 18 which resembles aportion of a toroid. the uppermost portion of this toroidal surfacedisposed tangent to a plane disposed perpen cularly with respect to theaxis of the snare plug. This inner construction may be modified to suitindividual requirements.

As in the first-described form, the sonically shaped electrode it isdisposed with its periph eral edge spaced from the opening in shell [0and is of slightly greater diameter than that opening. Preferably, inthe second-n1entioned modified form, the disc (4' is disposed within theskirt portion l5, this arrangement offering a more efiective barrier tothe entrance of undesirable combustion products into the interior of thespark plug.

In both forms of the device, the disc-shaped electrode performs atwofold function in it covers the opening in the end of the groundelectrode, offering obstructive resistance to the products of combustionwhich might otherwise foul the interior of the spark plug, and it servesto dissipate heat which would normally be absorbed by the insulator. Inthe second-mentioned form, the skirt portion also assists in theperformance of both these functions. The importance of heat-dissipationcannot be overemphasized, especially Where high-compression engines areconcerned. Spark plugs for these engines are required to be produced foruse in varying heat ranges, which necessitates the maintenance of largestocks of spark plugs by suppliers, whereas with the present invention,a single item may be used for several diilerent heat ranges.

Another advantage of the present invention is the fact that an externalspark is provided, rather than one that takes place in close proximityto the insulator and the interior of the spark Because of the shape ofthe disc-electrode and the configuration of the adjacent surface of theshell electrode, the raw vapors and the pro ucts of combustion in theengine cylinder are dire away from the insulator and the interior in adirection generally across the open end of the shell, instead of downinto the shell. In the first-mentioned modification the surface 55 isflat and disposed in a plane perpendicular to the axis of the insulatorand shell. In the second-mentioned modification, the surface 53 mergeswith the interior cylindrical wall it at the opening at the end of theshell id in a surface which is tangent to a plane perpendicular to theaxis of the insulator and shell. For convenience, it can be said thatboth surfaces l5 and i8 merge with the interior wall of the shellelectrode tangent to a plane perpendicular to the axis of the insulatorand shell, and that thereby the gases in this area will be directedacross the opening rather than into it.

Furthermore, the turbulence created by the gases passing through the airgap between the center electrode and the shell electrode assists in themixing of the gasoline with the air, and will also drive oilincombustible products, either solid or liquid, which might otherwiseadhere to the surface of the electrodes. The spark will also jump thegap in the restricted zone around the periphery of the disc electrodebecause there will be a lower pressure at this point than in the rest ofthe cylinder during the compression stroke.

In the spark plugs just described, the discs [4 and i i consist ofrelatively inflexible, but thinwalled, elements which are permanentlypositioned to provide a fixed air gap. This has the advantage that thegap may be set at the factory with precision. instruments and, becauserelatively little burning of the metal takes place at any one point,this gap will remain constant during the life of the spark plug. Butwhere it is desirable to provide an air gap which may be adjusted withinwide limits, it is preferred to use the type of disc electrode shown inFig. 5. In this modification the conically shaped element 252 isprovided with one or more radially extending slits along its periphery.The central portion of the disc 2% is secured as before to theprojecting end of rod or wire, such as i3, so as to position the disc inconjunction with a ground shell electrode, such as M, or M in the mannerpreviously described.

In making the slits 2!, the metal may be merely severed, or sheared, asby a cutting tool, or narrow radially extending portions of the metal beremoved, as by a die. In either the presence of the slits enables thedisc to be sonically distorted so as to alter the effective diameter ofthe disc. Such distortion will also be elfective to alter the lateralpositioning of the periphery of the disc with respect to the centrallysupported section. In the case of the modification shown in Figs. 1 and2, this lateral displacement of the periphery will alter its distancefrom the surface l5 of the ground electrode. In the case of themodification shown in Figs. 3 and i, the alteration of the diameter ofthe periphery of electrode 20 would alter the gap between it and thesurface ll of the skirt Hi. In either case the effect of conicaldistortion of electrode 20 is to alter the air gap between the twoelectrodes.

A modified form of skirt construction is shown in Fig. 6, which may beused in combination with a center electrode 25, similar in shape toeither the previously described electrodes. In this modification thecylindrically disposed shirt 25 may be provided with a number oflongitudinally disposed slots 2?, extending into the lower margin of theskirt. This type of skirt is particularly adapted for use with a fixedcenter electrode, inasmuch as the air gap between the electrodes may beadjusted by bending the arcuate portions 23, defined by the slots 2?.

'laving thus described several preferred forms of the invention, it willbe understood that they are illustrative only, and not intended to limitthe scope of the invention other than as claimed.

I claim:

In a spark plug having an open ended ground electrode shell, alongitudinally extending insulator disposed within the shell andprovided with a second electrode projecting beyond the end of theinsulator, said shell being provided with a substantially smoothcylindrical inner surface terminating at the open end of the shell, arelatively thin-walled cylindrical skirt portion projecting beyond theopen end of the shell and of greater diameter than the diameter of theinner surface of said shell, said second electrode being provided with aconically shaped portion having the circumferential edge disposed withinsaid skirt portion spaced from said opening, said second electrode beingalso provided with radially disposed slits to permit adjustment of thespark gap, and an annularly extending surface resembling a portion of atoroid extending between the opening in said shell and the inner surfaceof the skirt portion, said skirt portion being provided withlongitudinally extending slits to permit further adjustment of the sparkgap.

Name Date Herz May 23, 1905 Number Number Number Name Date Sander May14, 1907 Walton Mar. 23, 1915 Meaker Oct. 12, 1915 Campbell et a1. Dec.10, 1918 Main June 3, 1919 Dumbovich May 19, 1925 Hall June 20, 1939FOREIGN PATENTS Country Date Great Britain Sept. 6, 1920 Great BritainNov. 8, 1923 Great Britain Aug. 20, 1935

